Lens mold

Abstract: A lens mold includes first (1) and second mold (2) members respectively having a concave (3) surface and a convex surface (4) for defining therebetween a lens cavity. One of the first and second mold members is configured to mechanically engage a ring of excess lens material upon polymerization of the lens material. Alternately, one of the first and second mold members includes a material formed along the periphery of a lens cavity (5) which causes the ring of excess lens material thereto. Furthermore, one of the first and second mold members is formed of a relatively transparent plastic material and includes an outer surface having an optical finish to permit optical inspection of a lens located on one of the concave and convex surfaces. Alternately, one of the first and second mold members is formed of a relatively opaque plastic material and includes an inner surface having an optical finish to permit optical inspection of a lens located on one of the concave and convex surfaces.

Description: The present invention relates generally to the inspection of contact lenses, and more particularly, to a lens mold for use primarily in the manufacture of soft contact lenses. Conventionally, a soft contact lens may be cast using a two-sided mold in which one side of the mold includes a convex surface and the other side of the mold includes an opposing concave surface, and in which a cavity for forming the lens is defined by the opposing convex and concave surfaces: A lens is formed by placing a lens material on one of the convex and concave surfaces, bringing the two sides of the mold together to form the lens cavity and separating the two sides of the mold to expose the cast lens after polymerization of the lens material. Furthermore, techniques are generally known for controlling the adhesion of the cast lens upon separation of the two sides of the mold, i.e. for causing the cast lens to exhibit an affinity to adhere to one of the convex and concave surfaces upon separation of the two sides of the mold. The utilization of such techniques helps eliminate the time consuming, manual labor that is otherwise required in determining which surface the transparent cast lens has adhered to after separation of the two sides of the mold. For example, European Patent Application No.0367513 discloses a technique for ensuring that the cast lens remains in contact with one side of the mold by flame polishing the convex surface of the one side of the mold. Furthermore, United States Patent No.4,197,266 discloses that by fabricating the two sides of the mold with materials which, while both wettable, have different degrees of wettability, one can insure that the cast lens will adhere to the desired surface of the mold upon separation. Additionally, United States Patent No.4,150,073 discloses that the adhesion of the cast lens may be controlled by exposing a mold surface to monomeric vapors. However, in manufacturing the contact lens, lens material of a sufficient quantity to exceed the volume of the cavity is placed on one of the mold surfaces, and then the two sides to the mold are brought together to form the lens cavity. The WO 93/04848 describes that quantity of excess lens material is collected within the mold body, along the outer periphery of the lens cavity, to form a ring of excess polymerized lens material and, upon separation of the lens mold, this ring of excess lens material is located at one of the mold sides. Furthermore, after the lens has been cast and the mold separated, testing of certain physical characteristics of the cast lens must be carried out. Conventionally, the individual cast lens is manually removed from the mold, and placed on a test tray. Light is then transmitted through the cast lens and directed onto a screen where certain deformities in the cast lens may be visually detected. In general, the manufacture of contact lens is conventionally labor intensive, requiring manual handling and visual inspection of the cast lens during several stages of production, and further requiring manual removal of the ring of excess lens material. A general of the present invention is to provide a contact lens mold in which optical inspection of the lens may be carried out while the lens remains disposed on a mold surface to the contact lens mold. A more specific object of the present invention is to reduce the manual labor expended in the manufacture of contact lenses. A more specific object of the present invention is to provide a two-sided contact lens mold in which the ring of excess lens material surrounding the periphery of the mold cavity is engaged with a desired side of the two-sided mold upon separation of the two-sided mold. The above object of the present invention is realized by forming one side of the mold of a relatively transparent plastic material and by providing an optical finish on a bottom surface thereof. Optical inspection of a lens may be carried out by transmitting light through the one side of the mold and the lens disposed on the other side of the mold. The above and other objects of the present invention are further realized by forming one side of the mold of a relatively opaque plastic material and by providing an optical finish on an inner surface thereof. Optical inspection of a lens may be carried out by reflecting light off the inner surface and through the lens disposed on the inner surface. The aspects and features of the present invention will become more apparent from the following description taken in conjunction with the drawings in which: FIG. 1 is a sectional view of a two-sided lens mold according to one embodiment of the present invention; FIGs. 2a and 2b are sectional views for explaining the mechanical engagement of excess lens material to the two-sided lens mold of the present invention; FIGs. 3-8 are sectional views of a two-sided lens mold according to other embodiments of the present invention; FIGs. 9 and 10 are sectional views for explaining the utility of a contact lens mold according to another embodiment of the present invention. As shown in FIG.1, the two-sided lens mold of the present invention includes a first mold member1 having a concave surface portion3, and a second mold member2 having a convex surface portion4. A cavity5 for forming the lens is provided when the outer rim6 of the concave surface portion3 is made to contact the convex surface portion4 as shown. Such contact is achieved by engagement (such as by friction fitting members11 or by mechanical clamping) of the first and second mold members1, 2. The surfaces of the lens are thus formed in conformity with the respective surfaces of the convex and concave surface portions3, 4. The curvature of the lens, and thus the curvature of the convex and concave surface portions3, 4, are specified in advance to comply with optical requirements. The first and second mold members1, 2 may be formed by known techniques, such as by injection molding. Furthermore, the first and second mold members1, 2 may optionally be formed of different plastic materials having different degrees of wettability. That is, for example, the first mold member1 may be made from relatively polar plastic materials, and the second mold member2 may be made from relatively non-polar plastic materials. Alternately, the first mold member1 may be made from relatively non-polar plastic materials, and the second mold member2 may be made from relatively polar plastic materials. Examples of relatively polar plastic materials include polymethylmethacrylate, polyvinylchloride, polycarbonate, polyamide, polyurethane, polyester, polysulfone, polystyrene, polyphenyleneoxide, etc., or copolymers, or blends of like materials. Examples of relatively non-polar plastic materials include polypropylene, polyethylene, poly[methylpentene], etc. or copolymers, or blends of like materials. Accordingly, as those skilled in the art will appreciate, by the proper selection of the lens material and the polar and non-polar plastic materials of the first and second mold members1, 2, the lens may be directed to adhere to the desired surface (concave or convex) of the two-sided mold upon separation of the first and second mold members1, 2. Accordingly, as those skilled in the art will further appreciate, the relative polarity of the plastic mold materials selected will depend on the polarity of the lens material itself. Moreover, the degree of polarity of each plastic mold material is dependent upon the amount or number of polar groups that may occur in the polymer backbone or side chains. Therefore, two different mold materials having different relative polarities may be selected from the "relatively polar materials" listed above for respectively forming the mold members1, 2, to achieve the same desired effect. Similarly, two different mold materials may instead be selected from the "relatively non-polar materials" listed above. According to one embodiment of the present invention, the first mold member1 is provided with an annular surface9 extending upwardly and inwardly (i.e. q is less than 90°) towards a longitudinal axis15 from the outer rim6 of the concave surface portion3. That is, if the annular surface9 tapers inwardly at a constant angle as shown, the annular surface9 is frusto-conical. The engagement of excess lens material according to the present invention will now be described with reference to FIGs.2a and2b. During the manufacture of the contact lens, lens material of a sufficient quantity to exceed the volume defined by the cavity5 is placed on the concave surface portion3 or the convex surface portion4. The first mold member1 is moved relative the second mold member2 to form the cavity5. The quantity of lens material in excess of the volume defined by the cavity5 is collected along the - outer periphery of the cavity5 in the form of a ring8. Suppose, as described above, that the lens material and the plastic materials of the first and second members1, 2 shown in FIG.2a are selected such that the lens7 is directed to adhere to the convex surface portion4 of the second mold member2. Upon polymerization of the lens material, the first and second mold members1, 2 are separated to expose the cast lens7 as shown in FIG.2b. The cast lens7 adheres to the convex surface portion4 due to the selection of the lens material and the relatively non-polar and polar plastic materials of the first and second mold members 1, 2. For the same reasons that the lens7 tends to adhere to the second mold member2, the ring8 of excess lens material will also tend to adhere to the second mold member2. However, the ring8 of excess lens material is mechanically engaged with the first mold member1 due to the inwardly extending annular surface9. It is noted that the angle q of the inwardly extending annular surface9 may extend only very slightly inwardly to operate as intended. Accordingly, upon separation of the first and second mold members1, 2, the first mold member1 having the ring8 of excess lens material engaged therewith may be discarded, and the second mold member2 having the cast lens7 adhered to the convex surface portion4 may be conveyed to further processing steps without individual handling of the cast lens itself and without inspection and removal of the ring8 of excess lens material. Other embodiments of the ring engaging mechanism of the present invention will now be described with reference to FIGs.3-7. As shown in FIG.3, the annular surface9 may be provided such that q equals or nearly equals 90°. In the annular surface9 is formed a round under cut31. As the excess lens material polymerizes along the annular surface9, such excess lens material will form within the round under cut31 and will thus be mechanically engaged with the mold member1, As shown in FIG.5, a rectangular notch32 may be provided in place of or in addition to the round under cut31 shown in FIG.3. As shown in FIG.4, the annular surface9 is provided with an outwardly extending lip member33 for engaging the ring of excess lens material. The lip member33 may be formed at the lower edge of the annular surface9 as shown, or the lip member33 may be formed elsewhere along the annular surface9. As shown in FIG.6, the concave portion3 is further defined by an outwardly extending annular member34 having a lower surface35. The lower surface35 has formed thereon a ring engaging member36. The ring engaging member36 includes a portion extending inwardly and downwardly from the lower surface35 to form an annular void37 as shown. The excess lens material flows into the annular void37 and, upon polymerization, is thereby mechanically engaged with the mold member1. As shown in FIG.7, a non-mechanical locking arrangement is provided for engaging the excess lens material. Suppose again that the first mold member1 is made of a relatively non-polar material and the second mold member (not shown) is made of a relatively polar material, thereby causing a cast lens to adhere to the relatively polar material of the second member. According to one embodiment of the present invention, a sleeve38 is provided along the periphery of the outer rim6 of the first mold member1. By forming the sleeve of a relatively more polar material with respect to the relatively polar material of the second mold member, the ring of excess lens material will exhibit an affinity to adhere to the relatively more polar material of the sleeve38. Although several embodiments of the ring engaging mechanism of the present invention have been herein described with reference to FIGS.1-7, it is understood that those skilled in the art may contemplate other specific configurations without departing from the scope and spirit of the present invention. Moreover, although the embodiments discussed above illustrate the engagement of the ring of excess lens material to the concave portion of the mold, the ring of excess lens material may instead be directed to engage the convex side of the mold. For example, as shown in FIG.8, the convex portion4 may include the inwardly extending annular surface9 of the embodiment shown in Fig.1 for engaging the ring of excess lens material. Similarly, the other embodiments of the present invention may be applied to the convex portion of the mold. Still another feature of the present invention will be described with reference to FIG.9. Suppose, as discussed above with reference to FIGs2a and 2b, that the cast lens7 has adhered to the convex portion4 of the second mold member2. According to the embodiment shown in FIG.9, optical inspection of the cast lens7 may be carried out without removing the cast lens7 from the convex surface portion4. As shown in FIG.9, the second mold member2 is formed of a relatively transparent plastic and a bottom surface 10 thereof is provided with an optical finish. The thus formed second mold member2 is placed between a light source20 and a light receiving unit21, whereby light is transmitted from the light source20 (either directly or by reflection), through the second mold member2, through the cast lens7, and to the light receiving unit21. The light receiving unit21 may be a projection screen, in which case deformities in the cast lens7 and debris in the second mold member2 may be detected by visual inspection of the pattern cast on the projection screen. It is also contemplated that the light receiving unit21 may be a CCD image sensor apparatus in which deformities in the cast lens7 and debris in the second mold member2 are detected automatically. An alternative arrangement may be provided as shown in FIG.10, in which the second mold member2 is formed of a relatively opaque plastic and an upper surface40 thereof, including the convex surface, is provided with a reflective optical finish. The thus formed second mold member2 is placed in relation to the light source 20 and the light receiving unit21 such that light is reflected off of the upper surface40 and through the cast lens7 to the light receiving unit21. Deformities in the cast lens7 and debris in the second mold member2 can thus be detected in the same manner as discussed above with respect to FIG.9. As is known to those skilled in the art, the tooling members for forming the lens mold are provided with an optical finish, by polishing for example, only at surface portions thereof which conform to the lens defining surfaces of the lens mold. In the same manner, the optical finishes discussed above with respect to FIGs.9 and10 may be obtained. Furthermore, a spin cast method of manufacturing contact lenses is known in the art whereby only one mold member is utilized. Briefly, in such a method, a single mold member is provided with a quantity of lens material on a concave surface thereof and is then rotated, whereby centrifugal forces act on the lens material to form a contact lens. The aspects and advantages of the present invention as discussed above with respect to FIGs.9 and10 are equally applicable to such a mold member used in the spin cast technique. According to the lens mold of the present invention, a lens may be cast and optically inspected without manual handling of the lens itself. Furthermore, especially when the cast lens is made to adhere to one side of a two-sided mold, the ring of excess lens material may be directed to adhere to the other side of the two-sided mold. The present invention is not limited to applications involving a two-sided lens mold made of materials having different degrees of wettability. That is, the ring engaging mechanisms and the optically finished surfaces of the present invention may be utilized and the advantages realized even in the case where is no control of the adherence of the cast lens. Still furthermore, although the discussion above is directed primarily to soft contact lenses, the present invention is not seen to be so limited, and may be directed to the manufacture of any other polymeric lenses.

Claims: A lens mold comprising: a first mold member (1) comprising a concave portion (3), said concave portion (3) having a concave surface centered at a longitudinal axis of said first mold member (1), an outer rim (6) located along a periphery of said concave surface (3), and ring engaging means disposed adjacent said outer rim (6) for engaging, upon polymerization of a lens material within a lens cavity (5), excess lens material formed along an outer periphery of the lens cavity (5); and a second mold member (2) comprising a convex portion (4) having a convex surface, wherein the lens cavity (5) is defined between said concave and convex surfaces (3,4) when said outer rim (6) of said concave portion (3) of said first mold member (1) is made to contact said convex portion (4) of said second mold member (2); and upon polymerization of the lens material and upon a separation of said first and second mold members (1,2), the excess lens material is engaged with said first mold member (1), wherein said second mold member (2) is formed of a relatively transparent plastic material and comprises an outer surface opposite said convex surface (4), said outer surface having an optical finish to permit optical inspection of a lens (7) located on said convex surface (4) by transmitting light through said outer surface, said second mold member (2), said convex surface (4) and the lens (7), or wherein said second mold member (2) is formed of a relatively opaque plastic material, and wherein said convex surface (4) is provided with an optical finish to permit optical inspection of a lens (7) located on said convex surface (4) by reflecting light off of said convex surface (4) and through the lens (7). A lens mold according to claim 1, wherein said ring engaging means of said concave portion comprises an annular surface (9) extending inwardly towards the longitudinal axis of said first mold member (1) from said outer rim (6). A lens mold according to claim 2, wherein said annular surface (9) is frusto-conical. A lens mold according to claim 1, wherein said ring engaging means of said concave portion (3) comprises an annular surface (9) extending substantially parallel to the longitudinal axis of the first mold member (1), and a notch (31, 32) formed in and along said annular surface (9). A lens mold according to claim 4, wherein said notch (31) defines a void within said annular surface (9) having a rounded cross-section for receiving a portion of the excess lens material. A lens mold according to claim 4, wherein said notch (32) defines a void within said annular surface (9) having a rectangular cross-section for receiving a portion of the excess lens material. A lens mold according to claim 1, wherein said ring engaging means of said concave portion (3) comprises an annular surface (9) extending substantially parallel to the longitudinal axis of said first mold member (1), and a lip member (32) extending outwardly from said annular surface (9). A lens mold according to claim 1, wherein said ring engaging means of said concave portion (3) comprises a first annular surface extending (34) outwardly along the periphery of the lens cavity (5) from the outer rim (6), and an annular member (9) extending from said first annular surface (34), said annular member (9) defining a second annular surface extending inwardly towards the longitudinal axis of said first mold member (1) from said first annular surface (34), wherein an annular void for receiving the excess lens material is defined by said outer rim (6), said first annular surface (34) and said second annular surface (9). A lens mold according to claim 1, wherein said ring engaging means of said concave portion (3) comprises an annular member (9) made of a first plastic material disposed along a periphery of said outer rim (6), and wherein said second mold member (2) is made of a second plastic material, and wherein said first plastic material is more polar relative to said second plastic material, whereby the excess lens material will exhibit an affinity to adhere to said annular member (9) upon the separation of said first and second mold members (1,2). A lens mold according to claim 9, wherein said first mold member (1) at said concave surface (3) is made of a third plastic material, and wherein said second plastic material is more polar relative to said third plastic material, whereby a polymerized lens within the lens cavity (5) will exhibit an affinity to adhere to said convex surface (4) upon the separation of said first and second mold members (1, 2). A lens mold according to any one of claims1-8, wherein said first mold member (1) is made of a relatively non-polar plastic material, and said second mold member (2) is made of a relatively polar plastic material, whereby a polymerized lens within the lens cavity (5) will exhibit an affinity to adhere to said convex surface (4) upon the separation of said first and second mold members (1,2). A lens mold comprising: a first mold member (1) comprising a convex portion (4), said convex portion (4) having a convex surface (4) centered at a longitudinal axis of said first mold member (1), an outer rim (6) located along a periphery of said convex surface (4), and ring engaging means disposed adjacent said outer rim (6) for engaging, upon polymerization of a lens material within a lens cavity (5), excess lens material formed along an outer periphery of the lens cavity (5); and a second mold member (2) comprising a concave portion (3) having a concave surface (3), wherein the lens cavity (5) is defined between said convex and concave surfaces (3,4) when said outer rim (6) of said convex portion (4) of said first mold member (1) is made to contact said concave portion (3) of said second mold member (2); and upon polymerization of the lens material and upon a separation of said first and second mold members (1,2), the excess lens material is engaged with said first mold member (1), wherein said second mold member (2) is formed of a relatively transparent plastic material and comprises an outer surface opposite said concave surface (3), said outer surface having an optical finish to permit optical inspection of a lens (7) located on said concave surface (3) by transmitting light through said outer surface, said second mold member (2), said concave surface (3) and the lens (7), or wherein said second mold member (2) is formed of a relatively opaque plastic material, and wherein said concave surface (3) is provided with an optical finish to permit optical inspection of a lens (7) located on said concave surface (3) by reflecting light off of said concave (3) surface and through the lens (7). A lens mold according to claim 12, wherein said ring engaging means of said convex portion (4) comprises an annular surface (9) extending inwardly towards the longitudinal axis of said first mold member (1) from said outer rim (6). A lens mold according to claim 13, wherein said annular surface (9) is frustoconical. A lens mold according to claim 12, wherein said ring engaging means of said convex portion (4) comprises an annular surface (9) extending substantially parallel to the longitudinal axis of the first mold member (1), and a notch (31, 32) formed in and along said annular surface (9). A lens mold according to claim 15, wherein said notch (31) defines a void within said annular surface (9) having a rounded cross-section for receiving a portion of the excess lens material. A lens mold according to claim 15, wherein said notch (32) defines a void within said annular surface (9) having a rectangular cross-section for receiving a portion of the excess lens material. A lens mold according to claim 12, wherein said ring engaging means of said convex portion (4) comprises an annular surface (9) extending substantially parallel to the longitudinal axis of said first mold member (1), and a lip member (33) extending outwardly from said annular surface (9). A lens mold according to claim 12, wherein said ring engaging means of said convex portion (4) comprises a first annular surface (34) extending outwardly along the periphery of the lens cavity (5) from the outer rim (6), and an annular member (9) extending from said first annular surface (34), said annular member (9) defining a second annular surface extending inwardly towards the longitudinal axis of said first mold member (1) from said first annular surface (34), wherein an annular void for receiving the excess lens material is defined by said outer rim (6), first annular surface (34) and said second annular surface (9). A lens mold according to claim 12, wherein said ring engaging means of said convex portion (4) comprises an annular member (9) made of a first plastic material disposed along a periphery of said outer rim (6), and wherein said second mold member (2) is made of a second plastic material, and wherein said first plastic material is more polar relative to said second plastic material, whereby the excess lens material will exhibit an affinity to adhere to said annular member (9) upon the separation of said first and second mold members (1,2). A lens mold according to claim 20, wherein said first mold member (1) at said convex surface (4) is made of a third plastic material, and wherein said second plastic material is more polar relative to said third plastic material, whereby a polymerized lens (7) within the lens cavity (5) will exhibit an affinity to adhere to said concave surface (3) upon the separation of said first and second mold members (1,2). A lens mold according to claim 12, wherein said first mold member (1) is made of a relatively non-polar plastic material, and said second mold member (2) is made of a relatively polar plastic material, whereby a polymerized lens (7) within the lens cavity (5) will exhibit an affinity to adhere to said concave surface (3) upon the separation of said first and second mold members (1,2). A lens mold according to claim 1, comprising a mold member formed of a relatively transparent plastic material and having an outer surface opposite a convex surface (4), said outer surface having an optical finish to permit optical inspection of a lens (7) located on said convex surface (4) by transmitting light through said outer surface, said mold member, said convex surface and the lens (7). A lens mold according to claim 1, comprising a mold member formed of a relatively opaque plastic material and having a convex surface portion (4) defining a convex surface (4), said convex surface (4) having an optical finish to permit optical inspection of a lens (7) located on said convex surface (4) by reflecting light off said convex surface portion (4). A lens mold according to claim 1, comprising a mold member formed of a relatively transparent plastic material and having an outer surface opposite a concave surface (3), said outer surface having an optical finish to permit optical inspection of a lens (7) located on said concave surface (3) by transmitting light through said outer surface, said mold member, said concave surface (3) and the lens (7). A lens mold according to claim 1, comprising a mold member formed of a relatively opaque plastic material and having a concave surface portion defining a concave surface (3), said concave surface portion (3) having an optical finish to permit optical inspection of a lens (7) located on said concave surface (3) by reflecting light off of said concave surface portion (3).

Inventors: SIDDIQUI MUSHIR, SU KAI C, WHITE JACK C, SIDDIQUI, MUSHIR, SU, KAI C., WHITE, JACK C.
Applicants: NOVARTIS AG, NOVARTIS ERFIND VERWALT GMBH, NOVARTIS-ERFINDUNGEN VERWALTUNGSGESELLSCHAFT M.B.H.
Application year: 1994
Main classification: B29C33
IPC codes: B29C33, B29D11, B29C39, B29C35, G01M11, B29L11